| //===------ PPCLoopInstrFormPrep.cpp - Loop Instr Form Prep Pass ----------===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This file implements a pass to prepare loops for ppc preferred addressing |
| // modes, leveraging different instruction form. (eg: DS/DQ form, D/DS form with |
| // update) |
| // Additional PHIs are created for loop induction variables used by load/store |
| // instructions so that preferred addressing modes can be used. |
| // |
| // 1: DS/DQ form preparation, prepare the load/store instructions so that they |
| // can satisfy the DS/DQ form displacement requirements. |
| // Generically, this means transforming loops like this: |
| // for (int i = 0; i < n; ++i) { |
| // unsigned long x1 = *(unsigned long *)(p + i + 5); |
| // unsigned long x2 = *(unsigned long *)(p + i + 9); |
| // } |
| // |
| // to look like this: |
| // |
| // unsigned NewP = p + 5; |
| // for (int i = 0; i < n; ++i) { |
| // unsigned long x1 = *(unsigned long *)(i + NewP); |
| // unsigned long x2 = *(unsigned long *)(i + NewP + 4); |
| // } |
| // |
| // 2: D/DS form with update preparation, prepare the load/store instructions so |
| // that we can use update form to do pre-increment. |
| // Generically, this means transforming loops like this: |
| // for (int i = 0; i < n; ++i) |
| // array[i] = c; |
| // |
| // to look like this: |
| // |
| // T *p = array[-1]; |
| // for (int i = 0; i < n; ++i) |
| // *++p = c; |
| //===----------------------------------------------------------------------===// |
| |
| #define DEBUG_TYPE "ppc-loop-instr-form-prep" |
| |
| #include "PPC.h" |
| #include "PPCSubtarget.h" |
| #include "PPCTargetMachine.h" |
| #include "llvm/ADT/DepthFirstIterator.h" |
| #include "llvm/ADT/SmallPtrSet.h" |
| #include "llvm/ADT/SmallSet.h" |
| #include "llvm/ADT/SmallVector.h" |
| #include "llvm/ADT/Statistic.h" |
| #include "llvm/Analysis/LoopInfo.h" |
| #include "llvm/Analysis/ScalarEvolution.h" |
| #include "llvm/Analysis/ScalarEvolutionExpressions.h" |
| #include "llvm/IR/BasicBlock.h" |
| #include "llvm/IR/CFG.h" |
| #include "llvm/IR/Dominators.h" |
| #include "llvm/IR/Instruction.h" |
| #include "llvm/IR/Instructions.h" |
| #include "llvm/IR/IntrinsicInst.h" |
| #include "llvm/IR/IntrinsicsPowerPC.h" |
| #include "llvm/IR/Module.h" |
| #include "llvm/IR/Type.h" |
| #include "llvm/IR/Value.h" |
| #include "llvm/InitializePasses.h" |
| #include "llvm/Pass.h" |
| #include "llvm/Support/Casting.h" |
| #include "llvm/Support/CommandLine.h" |
| #include "llvm/Support/Debug.h" |
| #include "llvm/Transforms/Scalar.h" |
| #include "llvm/Transforms/Utils.h" |
| #include "llvm/Transforms/Utils/BasicBlockUtils.h" |
| #include "llvm/Transforms/Utils/Local.h" |
| #include "llvm/Transforms/Utils/LoopUtils.h" |
| #include "llvm/Transforms/Utils/ScalarEvolutionExpander.h" |
| #include <cassert> |
| #include <iterator> |
| #include <utility> |
| |
| using namespace llvm; |
| |
| static cl::opt<unsigned> MaxVarsPrep("ppc-formprep-max-vars", |
| cl::Hidden, cl::init(24), |
| cl::desc("Potential common base number threshold per function for PPC loop " |
| "prep")); |
| |
| static cl::opt<bool> PreferUpdateForm("ppc-formprep-prefer-update", |
| cl::init(true), cl::Hidden, |
| cl::desc("prefer update form when ds form is also a update form")); |
| |
| // Sum of following 3 per loop thresholds for all loops can not be larger |
| // than MaxVarsPrep. |
| // now the thresholds for each kind prep are exterimental values on Power9. |
| static cl::opt<unsigned> MaxVarsUpdateForm("ppc-preinc-prep-max-vars", |
| cl::Hidden, cl::init(3), |
| cl::desc("Potential PHI threshold per loop for PPC loop prep of update " |
| "form")); |
| |
| static cl::opt<unsigned> MaxVarsDSForm("ppc-dsprep-max-vars", |
| cl::Hidden, cl::init(3), |
| cl::desc("Potential PHI threshold per loop for PPC loop prep of DS form")); |
| |
| static cl::opt<unsigned> MaxVarsDQForm("ppc-dqprep-max-vars", |
| cl::Hidden, cl::init(8), |
| cl::desc("Potential PHI threshold per loop for PPC loop prep of DQ form")); |
| |
| |
| // If would not be profitable if the common base has only one load/store, ISEL |
| // should already be able to choose best load/store form based on offset for |
| // single load/store. Set minimal profitable value default to 2 and make it as |
| // an option. |
| static cl::opt<unsigned> DispFormPrepMinThreshold("ppc-dispprep-min-threshold", |
| cl::Hidden, cl::init(2), |
| cl::desc("Minimal common base load/store instructions triggering DS/DQ form " |
| "preparation")); |
| |
| STATISTIC(PHINodeAlreadyExistsUpdate, "PHI node already in pre-increment form"); |
| STATISTIC(PHINodeAlreadyExistsDS, "PHI node already in DS form"); |
| STATISTIC(PHINodeAlreadyExistsDQ, "PHI node already in DQ form"); |
| STATISTIC(DSFormChainRewritten, "Num of DS form chain rewritten"); |
| STATISTIC(DQFormChainRewritten, "Num of DQ form chain rewritten"); |
| STATISTIC(UpdFormChainRewritten, "Num of update form chain rewritten"); |
| |
| namespace { |
| struct BucketElement { |
| BucketElement(const SCEVConstant *O, Instruction *I) : Offset(O), Instr(I) {} |
| BucketElement(Instruction *I) : Offset(nullptr), Instr(I) {} |
| |
| const SCEVConstant *Offset; |
| Instruction *Instr; |
| }; |
| |
| struct Bucket { |
| Bucket(const SCEV *B, Instruction *I) : BaseSCEV(B), |
| Elements(1, BucketElement(I)) {} |
| |
| const SCEV *BaseSCEV; |
| SmallVector<BucketElement, 16> Elements; |
| }; |
| |
| // "UpdateForm" is not a real PPC instruction form, it stands for dform |
| // load/store with update like ldu/stdu, or Prefetch intrinsic. |
| // For DS form instructions, their displacements must be multiple of 4. |
| // For DQ form instructions, their displacements must be multiple of 16. |
| enum InstrForm { UpdateForm = 1, DSForm = 4, DQForm = 16 }; |
| |
| class PPCLoopInstrFormPrep : public FunctionPass { |
| public: |
| static char ID; // Pass ID, replacement for typeid |
| |
| PPCLoopInstrFormPrep() : FunctionPass(ID) { |
| initializePPCLoopInstrFormPrepPass(*PassRegistry::getPassRegistry()); |
| } |
| |
| PPCLoopInstrFormPrep(PPCTargetMachine &TM) : FunctionPass(ID), TM(&TM) { |
| initializePPCLoopInstrFormPrepPass(*PassRegistry::getPassRegistry()); |
| } |
| |
| void getAnalysisUsage(AnalysisUsage &AU) const override { |
| AU.addPreserved<DominatorTreeWrapperPass>(); |
| AU.addRequired<LoopInfoWrapperPass>(); |
| AU.addPreserved<LoopInfoWrapperPass>(); |
| AU.addRequired<ScalarEvolutionWrapperPass>(); |
| } |
| |
| bool runOnFunction(Function &F) override; |
| |
| private: |
| PPCTargetMachine *TM = nullptr; |
| const PPCSubtarget *ST; |
| DominatorTree *DT; |
| LoopInfo *LI; |
| ScalarEvolution *SE; |
| bool PreserveLCSSA; |
| |
| /// Successful preparation number for Update/DS/DQ form in all inner most |
| /// loops. One successful preparation will put one common base out of loop, |
| /// this may leads to register presure like LICM does. |
| /// Make sure total preparation number can be controlled by option. |
| unsigned SuccPrepCount; |
| |
| bool runOnLoop(Loop *L); |
| |
| /// Check if required PHI node is already exist in Loop \p L. |
| bool alreadyPrepared(Loop *L, Instruction* MemI, |
| const SCEV *BasePtrStartSCEV, |
| const SCEVConstant *BasePtrIncSCEV, |
| InstrForm Form); |
| |
| /// Collect condition matched(\p isValidCandidate() returns true) |
| /// candidates in Loop \p L. |
| SmallVector<Bucket, 16> |
| collectCandidates(Loop *L, |
| std::function<bool(const Instruction *, const Value *)> |
| isValidCandidate, |
| unsigned MaxCandidateNum); |
| |
| /// Add a candidate to candidates \p Buckets. |
| void addOneCandidate(Instruction *MemI, const SCEV *LSCEV, |
| SmallVector<Bucket, 16> &Buckets, |
| unsigned MaxCandidateNum); |
| |
| /// Prepare all candidates in \p Buckets for update form. |
| bool updateFormPrep(Loop *L, SmallVector<Bucket, 16> &Buckets); |
| |
| /// Prepare all candidates in \p Buckets for displacement form, now for |
| /// ds/dq. |
| bool dispFormPrep(Loop *L, SmallVector<Bucket, 16> &Buckets, |
| InstrForm Form); |
| |
| /// Prepare for one chain \p BucketChain, find the best base element and |
| /// update all other elements in \p BucketChain accordingly. |
| /// \p Form is used to find the best base element. |
| /// If success, best base element must be stored as the first element of |
| /// \p BucketChain. |
| /// Return false if no base element found, otherwise return true. |
| bool prepareBaseForDispFormChain(Bucket &BucketChain, |
| InstrForm Form); |
| |
| /// Prepare for one chain \p BucketChain, find the best base element and |
| /// update all other elements in \p BucketChain accordingly. |
| /// If success, best base element must be stored as the first element of |
| /// \p BucketChain. |
| /// Return false if no base element found, otherwise return true. |
| bool prepareBaseForUpdateFormChain(Bucket &BucketChain); |
| |
| /// Rewrite load/store instructions in \p BucketChain according to |
| /// preparation. |
| bool rewriteLoadStores(Loop *L, Bucket &BucketChain, |
| SmallSet<BasicBlock *, 16> &BBChanged, |
| InstrForm Form); |
| }; |
| |
| } // end anonymous namespace |
| |
| char PPCLoopInstrFormPrep::ID = 0; |
| static const char *name = "Prepare loop for ppc preferred instruction forms"; |
| INITIALIZE_PASS_BEGIN(PPCLoopInstrFormPrep, DEBUG_TYPE, name, false, false) |
| INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass) |
| INITIALIZE_PASS_DEPENDENCY(ScalarEvolutionWrapperPass) |
| INITIALIZE_PASS_END(PPCLoopInstrFormPrep, DEBUG_TYPE, name, false, false) |
| |
| static constexpr StringRef PHINodeNameSuffix = ".phi"; |
| static constexpr StringRef CastNodeNameSuffix = ".cast"; |
| static constexpr StringRef GEPNodeIncNameSuffix = ".inc"; |
| static constexpr StringRef GEPNodeOffNameSuffix = ".off"; |
| |
| FunctionPass *llvm::createPPCLoopInstrFormPrepPass(PPCTargetMachine &TM) { |
| return new PPCLoopInstrFormPrep(TM); |
| } |
| |
| static bool IsPtrInBounds(Value *BasePtr) { |
| Value *StrippedBasePtr = BasePtr; |
| while (BitCastInst *BC = dyn_cast<BitCastInst>(StrippedBasePtr)) |
| StrippedBasePtr = BC->getOperand(0); |
| if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(StrippedBasePtr)) |
| return GEP->isInBounds(); |
| |
| return false; |
| } |
| |
| static std::string getInstrName(const Value *I, StringRef Suffix) { |
| assert(I && "Invalid paramater!"); |
| if (I->hasName()) |
| return (I->getName() + Suffix).str(); |
| else |
| return ""; |
| } |
| |
| static Value *GetPointerOperand(Value *MemI) { |
| if (LoadInst *LMemI = dyn_cast<LoadInst>(MemI)) { |
| return LMemI->getPointerOperand(); |
| } else if (StoreInst *SMemI = dyn_cast<StoreInst>(MemI)) { |
| return SMemI->getPointerOperand(); |
| } else if (IntrinsicInst *IMemI = dyn_cast<IntrinsicInst>(MemI)) { |
| if (IMemI->getIntrinsicID() == Intrinsic::prefetch || |
| IMemI->getIntrinsicID() == Intrinsic::ppc_vsx_lxvp) |
| return IMemI->getArgOperand(0); |
| if (IMemI->getIntrinsicID() == Intrinsic::ppc_vsx_stxvp) |
| return IMemI->getArgOperand(1); |
| } |
| |
| return nullptr; |
| } |
| |
| bool PPCLoopInstrFormPrep::runOnFunction(Function &F) { |
| if (skipFunction(F)) |
| return false; |
| |
| LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo(); |
| SE = &getAnalysis<ScalarEvolutionWrapperPass>().getSE(); |
| auto *DTWP = getAnalysisIfAvailable<DominatorTreeWrapperPass>(); |
| DT = DTWP ? &DTWP->getDomTree() : nullptr; |
| PreserveLCSSA = mustPreserveAnalysisID(LCSSAID); |
| ST = TM ? TM->getSubtargetImpl(F) : nullptr; |
| SuccPrepCount = 0; |
| |
| bool MadeChange = false; |
| |
| for (auto I = LI->begin(), IE = LI->end(); I != IE; ++I) |
| for (auto L = df_begin(*I), LE = df_end(*I); L != LE; ++L) |
| MadeChange |= runOnLoop(*L); |
| |
| return MadeChange; |
| } |
| |
| void PPCLoopInstrFormPrep::addOneCandidate(Instruction *MemI, const SCEV *LSCEV, |
| SmallVector<Bucket, 16> &Buckets, |
| unsigned MaxCandidateNum) { |
| assert((MemI && GetPointerOperand(MemI)) && |
| "Candidate should be a memory instruction."); |
| assert(LSCEV && "Invalid SCEV for Ptr value."); |
| bool FoundBucket = false; |
| for (auto &B : Buckets) { |
| const SCEV *Diff = SE->getMinusSCEV(LSCEV, B.BaseSCEV); |
| if (const auto *CDiff = dyn_cast<SCEVConstant>(Diff)) { |
| B.Elements.push_back(BucketElement(CDiff, MemI)); |
| FoundBucket = true; |
| break; |
| } |
| } |
| |
| if (!FoundBucket) { |
| if (Buckets.size() == MaxCandidateNum) |
| return; |
| Buckets.push_back(Bucket(LSCEV, MemI)); |
| } |
| } |
| |
| SmallVector<Bucket, 16> PPCLoopInstrFormPrep::collectCandidates( |
| Loop *L, |
| std::function<bool(const Instruction *, const Value *)> isValidCandidate, |
| unsigned MaxCandidateNum) { |
| SmallVector<Bucket, 16> Buckets; |
| for (const auto &BB : L->blocks()) |
| for (auto &J : *BB) { |
| Value *PtrValue; |
| Instruction *MemI; |
| |
| if (LoadInst *LMemI = dyn_cast<LoadInst>(&J)) { |
| MemI = LMemI; |
| PtrValue = LMemI->getPointerOperand(); |
| } else if (StoreInst *SMemI = dyn_cast<StoreInst>(&J)) { |
| MemI = SMemI; |
| PtrValue = SMemI->getPointerOperand(); |
| } else if (IntrinsicInst *IMemI = dyn_cast<IntrinsicInst>(&J)) { |
| if (IMemI->getIntrinsicID() == Intrinsic::prefetch || |
| IMemI->getIntrinsicID() == Intrinsic::ppc_vsx_lxvp) { |
| MemI = IMemI; |
| PtrValue = IMemI->getArgOperand(0); |
| } else if (IMemI->getIntrinsicID() == Intrinsic::ppc_vsx_stxvp) { |
| MemI = IMemI; |
| PtrValue = IMemI->getArgOperand(1); |
| } else continue; |
| } else continue; |
| |
| unsigned PtrAddrSpace = PtrValue->getType()->getPointerAddressSpace(); |
| if (PtrAddrSpace) |
| continue; |
| |
| if (L->isLoopInvariant(PtrValue)) |
| continue; |
| |
| const SCEV *LSCEV = SE->getSCEVAtScope(PtrValue, L); |
| const SCEVAddRecExpr *LARSCEV = dyn_cast<SCEVAddRecExpr>(LSCEV); |
| if (!LARSCEV || LARSCEV->getLoop() != L) |
| continue; |
| |
| if (isValidCandidate(&J, PtrValue)) |
| addOneCandidate(MemI, LSCEV, Buckets, MaxCandidateNum); |
| } |
| return Buckets; |
| } |
| |
| bool PPCLoopInstrFormPrep::prepareBaseForDispFormChain(Bucket &BucketChain, |
| InstrForm Form) { |
| // RemainderOffsetInfo details: |
| // key: value of (Offset urem DispConstraint). For DSForm, it can |
| // be [0, 4). |
| // first of pair: the index of first BucketElement whose remainder is equal |
| // to key. For key 0, this value must be 0. |
| // second of pair: number of load/stores with the same remainder. |
| DenseMap<unsigned, std::pair<unsigned, unsigned>> RemainderOffsetInfo; |
| |
| for (unsigned j = 0, je = BucketChain.Elements.size(); j != je; ++j) { |
| if (!BucketChain.Elements[j].Offset) |
| RemainderOffsetInfo[0] = std::make_pair(0, 1); |
| else { |
| unsigned Remainder = |
| BucketChain.Elements[j].Offset->getAPInt().urem(Form); |
| if (RemainderOffsetInfo.find(Remainder) == RemainderOffsetInfo.end()) |
| RemainderOffsetInfo[Remainder] = std::make_pair(j, 1); |
| else |
| RemainderOffsetInfo[Remainder].second++; |
| } |
| } |
| // Currently we choose the most profitable base as the one which has the max |
| // number of load/store with same remainder. |
| // FIXME: adjust the base selection strategy according to load/store offset |
| // distribution. |
| // For example, if we have one candidate chain for DS form preparation, which |
| // contains following load/stores with different remainders: |
| // 1: 10 load/store whose remainder is 1; |
| // 2: 9 load/store whose remainder is 2; |
| // 3: 1 for remainder 3 and 0 for remainder 0; |
| // Now we will choose the first load/store whose remainder is 1 as base and |
| // adjust all other load/stores according to new base, so we will get 10 DS |
| // form and 10 X form. |
| // But we should be more clever, for this case we could use two bases, one for |
| // remainder 1 and the other for remainder 2, thus we could get 19 DS form and 1 |
| // X form. |
| unsigned MaxCountRemainder = 0; |
| for (unsigned j = 0; j < (unsigned)Form; j++) |
| if ((RemainderOffsetInfo.find(j) != RemainderOffsetInfo.end()) && |
| RemainderOffsetInfo[j].second > |
| RemainderOffsetInfo[MaxCountRemainder].second) |
| MaxCountRemainder = j; |
| |
| // Abort when there are too few insts with common base. |
| if (RemainderOffsetInfo[MaxCountRemainder].second < DispFormPrepMinThreshold) |
| return false; |
| |
| // If the first value is most profitable, no needed to adjust BucketChain |
| // elements as they are substracted the first value when collecting. |
| if (MaxCountRemainder == 0) |
| return true; |
| |
| // Adjust load/store to the new chosen base. |
| const SCEV *Offset = |
| BucketChain.Elements[RemainderOffsetInfo[MaxCountRemainder].first].Offset; |
| BucketChain.BaseSCEV = SE->getAddExpr(BucketChain.BaseSCEV, Offset); |
| for (auto &E : BucketChain.Elements) { |
| if (E.Offset) |
| E.Offset = cast<SCEVConstant>(SE->getMinusSCEV(E.Offset, Offset)); |
| else |
| E.Offset = cast<SCEVConstant>(SE->getNegativeSCEV(Offset)); |
| } |
| |
| std::swap(BucketChain.Elements[RemainderOffsetInfo[MaxCountRemainder].first], |
| BucketChain.Elements[0]); |
| return true; |
| } |
| |
| // FIXME: implement a more clever base choosing policy. |
| // Currently we always choose an exist load/store offset. This maybe lead to |
| // suboptimal code sequences. For example, for one DS chain with offsets |
| // {-32769, 2003, 2007, 2011}, we choose -32769 as base offset, and left disp |
| // for load/stores are {0, 34772, 34776, 34780}. Though each offset now is a |
| // multipler of 4, it cannot be represented by sint16. |
| bool PPCLoopInstrFormPrep::prepareBaseForUpdateFormChain(Bucket &BucketChain) { |
| // We have a choice now of which instruction's memory operand we use as the |
| // base for the generated PHI. Always picking the first instruction in each |
| // bucket does not work well, specifically because that instruction might |
| // be a prefetch (and there are no pre-increment dcbt variants). Otherwise, |
| // the choice is somewhat arbitrary, because the backend will happily |
| // generate direct offsets from both the pre-incremented and |
| // post-incremented pointer values. Thus, we'll pick the first non-prefetch |
| // instruction in each bucket, and adjust the recurrence and other offsets |
| // accordingly. |
| for (int j = 0, je = BucketChain.Elements.size(); j != je; ++j) { |
| if (auto *II = dyn_cast<IntrinsicInst>(BucketChain.Elements[j].Instr)) |
| if (II->getIntrinsicID() == Intrinsic::prefetch) |
| continue; |
| |
| // If we'd otherwise pick the first element anyway, there's nothing to do. |
| if (j == 0) |
| break; |
| |
| // If our chosen element has no offset from the base pointer, there's |
| // nothing to do. |
| if (!BucketChain.Elements[j].Offset || |
| BucketChain.Elements[j].Offset->isZero()) |
| break; |
| |
| const SCEV *Offset = BucketChain.Elements[j].Offset; |
| BucketChain.BaseSCEV = SE->getAddExpr(BucketChain.BaseSCEV, Offset); |
| for (auto &E : BucketChain.Elements) { |
| if (E.Offset) |
| E.Offset = cast<SCEVConstant>(SE->getMinusSCEV(E.Offset, Offset)); |
| else |
| E.Offset = cast<SCEVConstant>(SE->getNegativeSCEV(Offset)); |
| } |
| |
| std::swap(BucketChain.Elements[j], BucketChain.Elements[0]); |
| break; |
| } |
| return true; |
| } |
| |
| bool PPCLoopInstrFormPrep::rewriteLoadStores(Loop *L, Bucket &BucketChain, |
| SmallSet<BasicBlock *, 16> &BBChanged, |
| InstrForm Form) { |
| bool MadeChange = false; |
| const SCEVAddRecExpr *BasePtrSCEV = |
| cast<SCEVAddRecExpr>(BucketChain.BaseSCEV); |
| if (!BasePtrSCEV->isAffine()) |
| return MadeChange; |
| |
| LLVM_DEBUG(dbgs() << "PIP: Transforming: " << *BasePtrSCEV << "\n"); |
| |
| assert(BasePtrSCEV->getLoop() == L && "AddRec for the wrong loop?"); |
| |
| // The instruction corresponding to the Bucket's BaseSCEV must be the first |
| // in the vector of elements. |
| Instruction *MemI = BucketChain.Elements.begin()->Instr; |
| Value *BasePtr = GetPointerOperand(MemI); |
| assert(BasePtr && "No pointer operand"); |
| |
| Type *I8Ty = Type::getInt8Ty(MemI->getParent()->getContext()); |
| Type *I8PtrTy = Type::getInt8PtrTy(MemI->getParent()->getContext(), |
| BasePtr->getType()->getPointerAddressSpace()); |
| |
| if (!SE->isLoopInvariant(BasePtrSCEV->getStart(), L)) |
| return MadeChange; |
| |
| const SCEVConstant *BasePtrIncSCEV = |
| dyn_cast<SCEVConstant>(BasePtrSCEV->getStepRecurrence(*SE)); |
| if (!BasePtrIncSCEV) |
| return MadeChange; |
| |
| // For some DS form load/store instructions, it can also be an update form, |
| // if the stride is a multipler of 4. Use update form if prefer it. |
| bool CanPreInc = (Form == UpdateForm || |
| ((Form == DSForm) && !BasePtrIncSCEV->getAPInt().urem(4) && |
| PreferUpdateForm)); |
| const SCEV *BasePtrStartSCEV = nullptr; |
| if (CanPreInc) |
| BasePtrStartSCEV = |
| SE->getMinusSCEV(BasePtrSCEV->getStart(), BasePtrIncSCEV); |
| else |
| BasePtrStartSCEV = BasePtrSCEV->getStart(); |
| |
| if (!isSafeToExpand(BasePtrStartSCEV, *SE)) |
| return MadeChange; |
| |
| if (alreadyPrepared(L, MemI, BasePtrStartSCEV, BasePtrIncSCEV, Form)) |
| return MadeChange; |
| |
| LLVM_DEBUG(dbgs() << "PIP: New start is: " << *BasePtrStartSCEV << "\n"); |
| |
| BasicBlock *Header = L->getHeader(); |
| unsigned HeaderLoopPredCount = pred_size(Header); |
| BasicBlock *LoopPredecessor = L->getLoopPredecessor(); |
| |
| PHINode *NewPHI = |
| PHINode::Create(I8PtrTy, HeaderLoopPredCount, |
| getInstrName(MemI, PHINodeNameSuffix), |
| Header->getFirstNonPHI()); |
| |
| SCEVExpander SCEVE(*SE, Header->getModule()->getDataLayout(), "pistart"); |
| Value *BasePtrStart = SCEVE.expandCodeFor(BasePtrStartSCEV, I8PtrTy, |
| LoopPredecessor->getTerminator()); |
| |
| // Note that LoopPredecessor might occur in the predecessor list multiple |
| // times, and we need to add it the right number of times. |
| for (auto PI : predecessors(Header)) { |
| if (PI != LoopPredecessor) |
| continue; |
| |
| NewPHI->addIncoming(BasePtrStart, LoopPredecessor); |
| } |
| |
| Instruction *PtrInc = nullptr; |
| Instruction *NewBasePtr = nullptr; |
| if (CanPreInc) { |
| Instruction *InsPoint = &*Header->getFirstInsertionPt(); |
| PtrInc = GetElementPtrInst::Create( |
| I8Ty, NewPHI, BasePtrIncSCEV->getValue(), |
| getInstrName(MemI, GEPNodeIncNameSuffix), InsPoint); |
| cast<GetElementPtrInst>(PtrInc)->setIsInBounds(IsPtrInBounds(BasePtr)); |
| for (auto PI : predecessors(Header)) { |
| if (PI == LoopPredecessor) |
| continue; |
| |
| NewPHI->addIncoming(PtrInc, PI); |
| } |
| if (PtrInc->getType() != BasePtr->getType()) |
| NewBasePtr = new BitCastInst( |
| PtrInc, BasePtr->getType(), |
| getInstrName(PtrInc, CastNodeNameSuffix), InsPoint); |
| else |
| NewBasePtr = PtrInc; |
| } else { |
| // Note that LoopPredecessor might occur in the predecessor list multiple |
| // times, and we need to make sure no more incoming value for them in PHI. |
| for (auto PI : predecessors(Header)) { |
| if (PI == LoopPredecessor) |
| continue; |
| |
| // For the latch predecessor, we need to insert a GEP just before the |
| // terminator to increase the address. |
| BasicBlock *BB = PI; |
| Instruction *InsPoint = BB->getTerminator(); |
| PtrInc = GetElementPtrInst::Create( |
| I8Ty, NewPHI, BasePtrIncSCEV->getValue(), |
| getInstrName(MemI, GEPNodeIncNameSuffix), InsPoint); |
| |
| cast<GetElementPtrInst>(PtrInc)->setIsInBounds(IsPtrInBounds(BasePtr)); |
| |
| NewPHI->addIncoming(PtrInc, PI); |
| } |
| PtrInc = NewPHI; |
| if (NewPHI->getType() != BasePtr->getType()) |
| NewBasePtr = |
| new BitCastInst(NewPHI, BasePtr->getType(), |
| getInstrName(NewPHI, CastNodeNameSuffix), |
| &*Header->getFirstInsertionPt()); |
| else |
| NewBasePtr = NewPHI; |
| } |
| |
| // Clear the rewriter cache, because values that are in the rewriter's cache |
| // can be deleted below, causing the AssertingVH in the cache to trigger. |
| SCEVE.clear(); |
| |
| if (Instruction *IDel = dyn_cast<Instruction>(BasePtr)) |
| BBChanged.insert(IDel->getParent()); |
| BasePtr->replaceAllUsesWith(NewBasePtr); |
| RecursivelyDeleteTriviallyDeadInstructions(BasePtr); |
| |
| // Keep track of the replacement pointer values we've inserted so that we |
| // don't generate more pointer values than necessary. |
| SmallPtrSet<Value *, 16> NewPtrs; |
| NewPtrs.insert(NewBasePtr); |
| |
| for (auto I = std::next(BucketChain.Elements.begin()), |
| IE = BucketChain.Elements.end(); I != IE; ++I) { |
| Value *Ptr = GetPointerOperand(I->Instr); |
| assert(Ptr && "No pointer operand"); |
| if (NewPtrs.count(Ptr)) |
| continue; |
| |
| Instruction *RealNewPtr; |
| if (!I->Offset || I->Offset->getValue()->isZero()) { |
| RealNewPtr = NewBasePtr; |
| } else { |
| Instruction *PtrIP = dyn_cast<Instruction>(Ptr); |
| if (PtrIP && isa<Instruction>(NewBasePtr) && |
| cast<Instruction>(NewBasePtr)->getParent() == PtrIP->getParent()) |
| PtrIP = nullptr; |
| else if (PtrIP && isa<PHINode>(PtrIP)) |
| PtrIP = &*PtrIP->getParent()->getFirstInsertionPt(); |
| else if (!PtrIP) |
| PtrIP = I->Instr; |
| |
| GetElementPtrInst *NewPtr = GetElementPtrInst::Create( |
| I8Ty, PtrInc, I->Offset->getValue(), |
| getInstrName(I->Instr, GEPNodeOffNameSuffix), PtrIP); |
| if (!PtrIP) |
| NewPtr->insertAfter(cast<Instruction>(PtrInc)); |
| NewPtr->setIsInBounds(IsPtrInBounds(Ptr)); |
| RealNewPtr = NewPtr; |
| } |
| |
| if (Instruction *IDel = dyn_cast<Instruction>(Ptr)) |
| BBChanged.insert(IDel->getParent()); |
| |
| Instruction *ReplNewPtr; |
| if (Ptr->getType() != RealNewPtr->getType()) { |
| ReplNewPtr = new BitCastInst(RealNewPtr, Ptr->getType(), |
| getInstrName(Ptr, CastNodeNameSuffix)); |
| ReplNewPtr->insertAfter(RealNewPtr); |
| } else |
| ReplNewPtr = RealNewPtr; |
| |
| Ptr->replaceAllUsesWith(ReplNewPtr); |
| RecursivelyDeleteTriviallyDeadInstructions(Ptr); |
| |
| NewPtrs.insert(RealNewPtr); |
| } |
| |
| MadeChange = true; |
| |
| SuccPrepCount++; |
| |
| if (Form == DSForm && !CanPreInc) |
| DSFormChainRewritten++; |
| else if (Form == DQForm) |
| DQFormChainRewritten++; |
| else if (Form == UpdateForm || (Form == DSForm && CanPreInc)) |
| UpdFormChainRewritten++; |
| |
| return MadeChange; |
| } |
| |
| bool PPCLoopInstrFormPrep::updateFormPrep(Loop *L, |
| SmallVector<Bucket, 16> &Buckets) { |
| bool MadeChange = false; |
| if (Buckets.empty()) |
| return MadeChange; |
| SmallSet<BasicBlock *, 16> BBChanged; |
| for (auto &Bucket : Buckets) |
| // The base address of each bucket is transformed into a phi and the others |
| // are rewritten based on new base. |
| if (prepareBaseForUpdateFormChain(Bucket)) |
| MadeChange |= rewriteLoadStores(L, Bucket, BBChanged, UpdateForm); |
| |
| if (MadeChange) |
| for (auto &BB : L->blocks()) |
| if (BBChanged.count(BB)) |
| DeleteDeadPHIs(BB); |
| return MadeChange; |
| } |
| |
| bool PPCLoopInstrFormPrep::dispFormPrep(Loop *L, SmallVector<Bucket, 16> &Buckets, |
| InstrForm Form) { |
| bool MadeChange = false; |
| |
| if (Buckets.empty()) |
| return MadeChange; |
| |
| SmallSet<BasicBlock *, 16> BBChanged; |
| for (auto &Bucket : Buckets) { |
| if (Bucket.Elements.size() < DispFormPrepMinThreshold) |
| continue; |
| if (prepareBaseForDispFormChain(Bucket, Form)) |
| MadeChange |= rewriteLoadStores(L, Bucket, BBChanged, Form); |
| } |
| |
| if (MadeChange) |
| for (auto &BB : L->blocks()) |
| if (BBChanged.count(BB)) |
| DeleteDeadPHIs(BB); |
| return MadeChange; |
| } |
| |
| // In order to prepare for the preferred instruction form, a PHI is added. |
| // This function will check to see if that PHI already exists and will return |
| // true if it found an existing PHI with the matched start and increment as the |
| // one we wanted to create. |
| bool PPCLoopInstrFormPrep::alreadyPrepared(Loop *L, Instruction* MemI, |
| const SCEV *BasePtrStartSCEV, |
| const SCEVConstant *BasePtrIncSCEV, |
| InstrForm Form) { |
| BasicBlock *BB = MemI->getParent(); |
| if (!BB) |
| return false; |
| |
| BasicBlock *PredBB = L->getLoopPredecessor(); |
| BasicBlock *LatchBB = L->getLoopLatch(); |
| |
| if (!PredBB || !LatchBB) |
| return false; |
| |
| // Run through the PHIs and see if we have some that looks like a preparation |
| iterator_range<BasicBlock::phi_iterator> PHIIter = BB->phis(); |
| for (auto & CurrentPHI : PHIIter) { |
| PHINode *CurrentPHINode = dyn_cast<PHINode>(&CurrentPHI); |
| if (!CurrentPHINode) |
| continue; |
| |
| if (!SE->isSCEVable(CurrentPHINode->getType())) |
| continue; |
| |
| const SCEV *PHISCEV = SE->getSCEVAtScope(CurrentPHINode, L); |
| |
| const SCEVAddRecExpr *PHIBasePtrSCEV = dyn_cast<SCEVAddRecExpr>(PHISCEV); |
| if (!PHIBasePtrSCEV) |
| continue; |
| |
| const SCEVConstant *PHIBasePtrIncSCEV = |
| dyn_cast<SCEVConstant>(PHIBasePtrSCEV->getStepRecurrence(*SE)); |
| if (!PHIBasePtrIncSCEV) |
| continue; |
| |
| if (CurrentPHINode->getNumIncomingValues() == 2) { |
| if ((CurrentPHINode->getIncomingBlock(0) == LatchBB && |
| CurrentPHINode->getIncomingBlock(1) == PredBB) || |
| (CurrentPHINode->getIncomingBlock(1) == LatchBB && |
| CurrentPHINode->getIncomingBlock(0) == PredBB)) { |
| if (PHIBasePtrIncSCEV == BasePtrIncSCEV) { |
| // The existing PHI (CurrentPHINode) has the same start and increment |
| // as the PHI that we wanted to create. |
| if (Form == UpdateForm && |
| PHIBasePtrSCEV->getStart() == BasePtrStartSCEV) { |
| ++PHINodeAlreadyExistsUpdate; |
| return true; |
| } |
| if (Form == DSForm || Form == DQForm) { |
| const SCEVConstant *Diff = dyn_cast<SCEVConstant>( |
| SE->getMinusSCEV(PHIBasePtrSCEV->getStart(), BasePtrStartSCEV)); |
| if (Diff && !Diff->getAPInt().urem(Form)) { |
| if (Form == DSForm) |
| ++PHINodeAlreadyExistsDS; |
| else |
| ++PHINodeAlreadyExistsDQ; |
| return true; |
| } |
| } |
| } |
| } |
| } |
| } |
| return false; |
| } |
| |
| bool PPCLoopInstrFormPrep::runOnLoop(Loop *L) { |
| bool MadeChange = false; |
| |
| // Only prep. the inner-most loop |
| if (!L->isInnermost()) |
| return MadeChange; |
| |
| // Return if already done enough preparation. |
| if (SuccPrepCount >= MaxVarsPrep) |
| return MadeChange; |
| |
| LLVM_DEBUG(dbgs() << "PIP: Examining: " << *L << "\n"); |
| |
| BasicBlock *LoopPredecessor = L->getLoopPredecessor(); |
| // If there is no loop predecessor, or the loop predecessor's terminator |
| // returns a value (which might contribute to determining the loop's |
| // iteration space), insert a new preheader for the loop. |
| if (!LoopPredecessor || |
| !LoopPredecessor->getTerminator()->getType()->isVoidTy()) { |
| LoopPredecessor = InsertPreheaderForLoop(L, DT, LI, nullptr, PreserveLCSSA); |
| if (LoopPredecessor) |
| MadeChange = true; |
| } |
| if (!LoopPredecessor) { |
| LLVM_DEBUG(dbgs() << "PIP fails since no predecessor for current loop.\n"); |
| return MadeChange; |
| } |
| // Check if a load/store has update form. This lambda is used by function |
| // collectCandidates which can collect candidates for types defined by lambda. |
| auto isUpdateFormCandidate = [&] (const Instruction *I, |
| const Value *PtrValue) { |
| assert((PtrValue && I) && "Invalid parameter!"); |
| // There are no update forms for Altivec vector load/stores. |
| if (ST && ST->hasAltivec() && |
| PtrValue->getType()->getPointerElementType()->isVectorTy()) |
| return false; |
| // There are no update forms for P10 lxvp/stxvp intrinsic. |
| auto *II = dyn_cast<IntrinsicInst>(I); |
| if (II && ((II->getIntrinsicID() == Intrinsic::ppc_vsx_lxvp) || |
| II->getIntrinsicID() == Intrinsic::ppc_vsx_stxvp)) |
| return false; |
| // See getPreIndexedAddressParts, the displacement for LDU/STDU has to |
| // be 4's multiple (DS-form). For i64 loads/stores when the displacement |
| // fits in a 16-bit signed field but isn't a multiple of 4, it will be |
| // useless and possible to break some original well-form addressing mode |
| // to make this pre-inc prep for it. |
| if (PtrValue->getType()->getPointerElementType()->isIntegerTy(64)) { |
| const SCEV *LSCEV = SE->getSCEVAtScope(const_cast<Value *>(PtrValue), L); |
| const SCEVAddRecExpr *LARSCEV = dyn_cast<SCEVAddRecExpr>(LSCEV); |
| if (!LARSCEV || LARSCEV->getLoop() != L) |
| return false; |
| if (const SCEVConstant *StepConst = |
| dyn_cast<SCEVConstant>(LARSCEV->getStepRecurrence(*SE))) { |
| const APInt &ConstInt = StepConst->getValue()->getValue(); |
| if (ConstInt.isSignedIntN(16) && ConstInt.srem(4) != 0) |
| return false; |
| } |
| } |
| return true; |
| }; |
| |
| // Check if a load/store has DS form. |
| auto isDSFormCandidate = [] (const Instruction *I, const Value *PtrValue) { |
| assert((PtrValue && I) && "Invalid parameter!"); |
| if (isa<IntrinsicInst>(I)) |
| return false; |
| Type *PointerElementType = PtrValue->getType()->getPointerElementType(); |
| return (PointerElementType->isIntegerTy(64)) || |
| (PointerElementType->isFloatTy()) || |
| (PointerElementType->isDoubleTy()) || |
| (PointerElementType->isIntegerTy(32) && |
| llvm::any_of(I->users(), |
| [](const User *U) { return isa<SExtInst>(U); })); |
| }; |
| |
| // Check if a load/store has DQ form. |
| auto isDQFormCandidate = [&] (const Instruction *I, const Value *PtrValue) { |
| assert((PtrValue && I) && "Invalid parameter!"); |
| // Check if it is a P10 lxvp/stxvp intrinsic. |
| auto *II = dyn_cast<IntrinsicInst>(I); |
| if (II) |
| return II->getIntrinsicID() == Intrinsic::ppc_vsx_lxvp || |
| II->getIntrinsicID() == Intrinsic::ppc_vsx_stxvp; |
| // Check if it is a P9 vector load/store. |
| return ST && ST->hasP9Vector() && |
| (PtrValue->getType()->getPointerElementType()->isVectorTy()); |
| }; |
| |
| // intrinsic for update form. |
| SmallVector<Bucket, 16> UpdateFormBuckets = |
| collectCandidates(L, isUpdateFormCandidate, MaxVarsUpdateForm); |
| |
| // Prepare for update form. |
| if (!UpdateFormBuckets.empty()) |
| MadeChange |= updateFormPrep(L, UpdateFormBuckets); |
| |
| // Collect buckets of comparable addresses used by loads and stores for DS |
| // form. |
| SmallVector<Bucket, 16> DSFormBuckets = |
| collectCandidates(L, isDSFormCandidate, MaxVarsDSForm); |
| |
| // Prepare for DS form. |
| if (!DSFormBuckets.empty()) |
| MadeChange |= dispFormPrep(L, DSFormBuckets, DSForm); |
| |
| // Collect buckets of comparable addresses used by loads and stores for DQ |
| // form. |
| SmallVector<Bucket, 16> DQFormBuckets = |
| collectCandidates(L, isDQFormCandidate, MaxVarsDQForm); |
| |
| // Prepare for DQ form. |
| if (!DQFormBuckets.empty()) |
| MadeChange |= dispFormPrep(L, DQFormBuckets, DQForm); |
| |
| return MadeChange; |
| } |
